This invention relates to a floating wick-holder which in use floats upon a body of combustible oil.
It has hitherto been known to make floating wick-holders by injection moulding from a single sheet of plastics material and to provide air-containing buoyancy chambers to enable the holder to float.
U.S. Pat. No. 3,183,688 (Sobelson) is an example of a wick-holder of the kind referred to above. It is a disc-like body formed from a single sheet of plastics material. It consists of a central wick support, a circular well portion defined by the inner surface of an annular rib, and an annular flotation portion defined between an outer wall of the wick-holder and the outer surface of the annular rib. The Sobelson wick-holder suffers from the disadvantages that in use the inner surface of the annular rib is in direct contact with the hot liquid in the well portion and that the upper bight portion of the annular rib is clear of the surface of the liquid and is exposed to the flame from the wick which is relatively close thereto. The annular flotation portion is open to the upperside and is liable to fill with liquid if the surface of the liquid is disturbed mechanically or by air currents with the result that the member can easily be made to sink. Furthermore, Sobelson is restricted to wick-holders of circular shape whereas consumers often desire more decorative shapes.
German DAS 1 077163 (Glafey) shows a flower-shaped wick-holder in which a plurality of petal members are fixed around a circular stamen portion containing a wick support. Each petal has an internal flotation cavity open to the underside thereof. In use the Glafey wick-holder floats with the stamen portion submerged. Although the idea of providing buoyancy by means of air trapped in flotation cavities beneath the wick-holder reduces the risk of the wick-holder sinking, there is still a risk of it doing so, and more importantly the requirement for flotation cavities imposes a practical lower limit on the size of the petals. Thus the Glafey wick-holder cannot be used to reproduce flower shapes or complex abstract shapes consisting wholly of fine filaments because flotation cavities have to be provided.
Another construction of wick-holder described in British patent specification No. 1,380,358 issued to RIZLA LIMITED consists of an imperforate, circular, one-piece, thin-walled member of a plastics material such as cellulose acetate, P.V.C. polystyrene or polypropylene, the member having a wall thickness of between 0.01 and 0.02 and preferably 0.015 inches. It is illustrated in FIGS. 5 and 6 which are plan and cross-sectional views of an embodiment of the wick-holder described in the said British patent.
In the device shown in FIGS. 5 and 6, the member 10 is moulded or vacuum-formed so as to have four portions 30 which define segmental flotation cavities opening to the underside of the member and separated by a flat area 20 which is cruciform in plan and which is below the level of the rims of the portions 30. When the member is set upon the surface 50 of a body of combustible oil, on which the member is caused to float because of the buoyancy-imparting effect of air trapped in the cavities 30, oil flows over the flat area to feed a wick W. The wick is supported in a recess within a tube 40 which projects down from the underside of the flat area and is located at the centre of the member. In use, the body of oil is supported on a non-flammable liquid such as water so that when the oil is exhausted the water floods over the flat area and extinguishes the wick. Because buoyancy is imparted to the member by trapped air there is again a reduced but not negligible chance of the member capsizing. More importantly the fact that the wick-holder is formed from a single circular sheet and the requirement for buoyancy chambers precludes the use of complex and artistically desirable shapes.